package qiti;

public class demo4por {

    public static void main(String[] args) {

        demo4 circle = new demo4();

        circle.r = 10;

        circle.area();
        double pai = 3.1415926;
        double s = circle.area2(pai);
        System.out.println("半径为" + circle.r
                + "的圆,面积为" + s);


    }

}